From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 077DDC433E2 for ; Mon, 7 Sep 2020 10:03:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C770B21531 for ; Mon, 7 Sep 2020 10:03:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=baylibre-com.20150623.gappssmtp.com header.i=@baylibre-com.20150623.gappssmtp.com header.b="ugGVMJW5" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728434AbgIGKDH (ORCPT ); Mon, 7 Sep 2020 06:03:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58366 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728400AbgIGKDF (ORCPT ); Mon, 7 Sep 2020 06:03:05 -0400 Received: from mail-ed1-x542.google.com (mail-ed1-x542.google.com [IPv6:2a00:1450:4864:20::542]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A8211C061574 for ; Mon, 7 Sep 2020 03:03:04 -0700 (PDT) Received: by mail-ed1-x542.google.com with SMTP id c10so12178163edk.6 for ; Mon, 07 Sep 2020 03:03:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=baylibre-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=eu0tVdC2SapQmxPGnrOiQAZ5HG6pSAsS9H4UlH7DET8=; b=ugGVMJW5RJbLvOkkPTzMtesjDjGP+0VKjWNbvyeyw2RAMXE6OInFtbSWjFRmI2mEZS Qsd8ZTpoPGy21huaFxq7lp3WRwdQ2JfnmeqB9iOMeg5qjFXrc5D3naTXSyS3YuGEFwBm oRbHf7veaLO0JOYUz/DRU9qgAEXENey2/qrOyy7qen1h8LeM1btTG83H6yE/8QPWql7s PzxcpQ97iEe6gy1nn1Kp/keE93njE+5j0WNLrCc2AomoVHBqeHFuwlm8+z6haucaxF0Z 72HZWjDalObdCuk9FIuI/j7BVINn0EVKCXAj8MCKTFXVU4ebqr3a2n1HRESpqbxbLXcv oUoA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=eu0tVdC2SapQmxPGnrOiQAZ5HG6pSAsS9H4UlH7DET8=; b=bKjEerM66i8++zZBxHa8zjGQKxxk41BtmjLFuGV4ARWJyoqbSTzPgpNuO8xrKsZ6iC R9dsnYpFme0yW6sXEiT5MxPpPCE/WORvr5AJJErlKlcHQU69o6X1Rqs37eHgWDj4lWMG 7TgQX59LDXz44TlWy1y7gs81/2IXNjgqerSC5hL8rUF5G19gOaCS1/YqUPjRfqMb8ONc uR28fgkPQPf4+l2P927bffnTotcBvlYb8RdbMHTJj0PghJSvbVMlNpdszwFZzicqL5LM QIOSs6F7fAzkAoZNy1vFccETlnFMPKvRmp3DSoWlItT1gIn+Aqf8HRCl4Nt5VoEgrnUf Lo8A== X-Gm-Message-State: AOAM530ppwFacHBxTyHoh4Ks0XlcUr++5YIIXXBOYwLr5vKmB/a/RXQM o4LK7EMNdRtrX/kHWZCz1xdQPhUUJitCJ9KWTNJLVg== X-Google-Smtp-Source: ABdhPJyHe8iRM84KrK6dTuGNdpxVVoq6lwssCgqCJnFgT/lL4ex/fl0tLxkqjF/9CuLd6Vxm+bMEsR7nsnt/D2ZfdeU= X-Received: by 2002:a50:d809:: with SMTP id o9mr20387639edj.12.1599472983149; Mon, 07 Sep 2020 03:03:03 -0700 (PDT) MIME-Version: 1.0 References: <20200904154547.3836-1-brgl@bgdev.pl> <20200904154547.3836-4-brgl@bgdev.pl> <20200904163517.GW1891694@smile.fi.intel.com> In-Reply-To: <20200904163517.GW1891694@smile.fi.intel.com> From: Bartosz Golaszewski Date: Mon, 7 Sep 2020 12:02:52 +0200 Message-ID: Subject: Re: [PATCH 03/23] lib: uaccess: provide getline_from_user() To: Andy Shevchenko Cc: Bartosz Golaszewski , Linus Walleij , Jonathan Corbet , Mika Westerberg , Kent Gibson , linux-gpio , linux-doc , LKML , linux-acpi@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Fri, Sep 4, 2020 at 6:35 PM Andy Shevchenko wrote: > > On Fri, Sep 04, 2020 at 05:45:27PM +0200, Bartosz Golaszewski wrote: > > From: Bartosz Golaszewski > > > > Provide a uaccess helper that allows callers to copy a single line from > > user memory. This is useful for debugfs write callbacks. > > Doesn't mm/util.c provides us something like this? > strndup_user()? > Yes, there's both strndup_user() as well as strncpy_from_user(). The problem is that they rely on the strings being NULL-terminated. This is not guaranteed for debugfs file_operations write callbacks. We need some helper that takes the minimum of bytes provided by userspace and the buffer size and figure out how many bytes to actually copy IMO. Bart